North and northwest Madagascar (from Ambodivahibe to Sahamalaza)

Location / Description / Jurisdiction / Features of Potential Outstanding Universal Values / Threats / Management / Geographic scale, integrity and site type / Other sites in the region / Key References

Location map for the bays and islands of northern Madagascar.
© David Obura

Location - The site is located in the north and northwest of Madagascar from from Loky/Ambodivahibe bays, around the tip of Cap d’Ambre, to the Bay of Sahamalaza/Radama to the west, and from the coastal terrestrial habitats to deep water at the 200 m contour.

Description - The northern tip of Madagascar has a unique mix of marine habitats due to opposing physical and oceanographic features on the east and the west sides. The site covers the continental shelf from the coastline to the border of the shelf, encompassing many different types of shelves, bays and islands. In the east, the narrow steep continental shelf results in narrow deep bays with canyons leading into deep water, experiencing strong upwelling (Ambodivahibe and Loky bays). In the west, a broad shallow bank rings the coast with a fossil reef at its edge, currently at 70 m depth, sheltering large bay systems such as Narindra, Mahajamba and Ramanetaka – Sahamalaza. On both sides, the bays contain mixed habitats of coral reefs, mangroves and seagrass beds. Offshore of the west coast is the shallow submerged Castor bank, with the edge of the bank at 30-50 m, and shallowest depths of 10 m.
Complex island systems are found on the west coast, including Nosy Mitsio, Nosy Hara, Nosy Tanikely (and the principal island of Nosy Be), being of different origins including volcanic (contemporary with Montagne d’Ambre), karstic (eroded reef structures) and sedimentary.
The northern tip of Madagascar is at the upstream end of the peak biodiversity region of the Indian Ocean, second only to the Coral Triangle in diversity of shallow marine species. Not only is it an important part of this region, its geology and oceanography may be key triggers for ocean-climate interactions, and upstream source reefs for marine species, for this high diversity region.

Jurisdiction – Madagascar

Features of Potential Outstanding Universal Values

Criterion viii - Geology and oceanography
Geology: the coastlines of the northern tip of Madagascar are passive continental margins, parts of Gondwana at one time connected to Africa on the west and India to the east. The western shelf edge is bordered by an ancient submerged barrier reef along its length of 500-700 km. The ‘tsingy’ rock formations, sharply eroded limestone spikes characteristic of Madagascar are well developed at sites on the west coast.
Oceanography: the tip of Madagascar may be one of the most important features determining the oceanography of East African and Mozambique channel coasts. It forces a venturi-like acceleration and vorticity on the South Equatorial Current, contributing to meso-scale variability expressed as fronts (Glorioso Front) and eddies in the northern Mozambique channel. These eddies dominate the oceanographic and biological processes of the channel.
Ocean-climate interations: the upwelling of cold deeper waters on the NE coast, particularly in Ambodivahibe bay may protect corals there from warming temperatures, while the warm conditions, high-turbidity and highly variable eddy conditions on the NW coast result in a complex mosaic of low- and high-impact sites during coral bleaching events.

Criterion ix – Ecology, species and evolution
The site is a mosaic of rich ecosystems: coral reefs, coral banks, mangroves, and seagrasses, and volcanic, karst or coral islands and islets, bays. A new synthesis proposes that the northern Mozambique Channel is a museum maintaining species over tens of millions of years due to its relative stability compared to other parts of the WIO: the coastlines are some of the oldest in the Indian Ocean (180 my), the climate of the region has remained stable during the Tertiary (67 mya to present), their structure results in little habitat change with changing sea levels, and ocean currents both bring species into the region and maintain high levels of connectivity, reducing chances of extinction. 
Connectivity: as the upstream end of the core high biodiversity region for the WIO, this region is critically important for larval supply to downstream reefs, and thus for recovery following disturbances and in a connected network of MPAs.

Criterion x - Habitats & conservation
Mangroves: the region contains the largest, and some of the most important mangroves in Madagascar - Sahamalaza Bay (10,000 ha) Sambirano delta (10,000 h) Ifasy delta (15,000 ha), Mahavavy north (15,000 ha).
Coral reefs: on the northeast and northwest coasts, reef environments are very different. The east is bathed by cool clear oceanic waters of the SEC, with strong upwelling. The west is in the lee of the SEC, in the warm waters of the anticyclonic eddies in the NE Mozambique channel, and due to high rainfall, experiences high-sediment conditions for reefs. The reefs are in the northern Mozambique Channel center of diversity for the WIO, so harbour the highest diversity of corals in the region (> 300 coral species), along with the northern Mozambique coast. The reefs also harbour 525 species of molluscs of with 11 species are restricted to the Indian Ocean and 463 species of fishes with about 30 species confined to Madagascar and adjacent regions and 8 species presently known only from the seas of Madagascar.
Birds: the area is a major seabird area for the western Indian Ocean. Important sites for several species of seagulls (Sterna  bengalensis, S. dougallii and S.  bergii); priority importance of karst habitat islands for Madagascar fish eagle Haliaeetus vociferoides, endemic to Madagascar (the only species of diurnal raptor listed in critical condition (CR) in Africa (in 2008). The Mitsio archipelago has significant numbers of brown booby (very rare in the WIO), frigate birds, brown noddies, and others.
Turtles: though data is sparse, there are many nesting sites for green and hawksbillturtles on the beaches of the islands.
Sharks: the Mitsio archipelago and Ramada have high species diversity including, grey reef, white tip, silvertip, zebra (Stegostoma fasciatum), scalloped hammerhead (in particular in September and October) and tawny nurse sharks. Guitarfish (Rhynchobatus djiddensis) are relatively common in the marine reserve of Nosy Tanikely. Shark populations are severely depleted throughout the region.
Dugong: probable presence of the last populations of dugong in Madagascar, with recent sightings in the NW between Mahajanga and Nosy Be; fishers indicate scattered reports in Nosy Mitsio.
Dolphins and cetaceans: abundant coastal dolphins in near shore waters of Nosy Be, Nosy Komba, Nosy Faly and the main coast of Madagascar. High diversity of cetaceans offshore at the shelf drop, very vulnerable to offshore petroleum development impacts. Significant migratory route for humpback whales on the NE coast.

Whale shark (R. typus) off Nosy Sakatia
© Jeremy Kiszka

Threats - Coastal traditional and industrial fisheries pose a high degree of threat particularly to the west coast as conditions are often calm. Overexploitation occurs of many marine resources, including holothurians, and molluscs, as well as sea turtles, dugongs, sharks and rays, and birds eggs. On the west coast and in Antsiranana bay, habitat destruction by dredging, and pollution are growing problems. Sedimentation is one of the most serious problems, particularly for coral reefs off the west coast. The west coast has a high susceptibility to climate change as conditions are hot throughout the year, though water turbidity and variability, and upwelling on the east coast may reduce the threat of climate change. Cyclones are a threat to both coastlines. In general, the health of different parts of the area is very patchy, with sites of high degradation interspersed with sites expressing the superlative geology, oceanography and biodiversity of the area.

Management status - There are a range of management actions already in place in the region with several existing MPAs (Nosy Hara, Nosy Tanikely, Sahamalaza), future MPAs (Nosy Mitsio, Nosy Iranja) and regulated areas for fisheries management (e.g. Biologically Sensitive Shrimp Areas of Ambaro Bay), providing a foundation for higher levels of protection, and more attention to ecosystem services provided by the marine environment. Both Nosy Hara and Sahamalaza-Radama islands National Park are Biosphere Reserves. Ambodivahibe is the focus of a community conservation and climate change protected area. Loky Bay and nearby Nosy Ankao are also the subject of conservation area planning, with local communities and private sector stakeholders, with prospects for limiting fishing and seabird depredation.
Many sites have cultural and historical importance (Nosy Hara, Nosy Mitsio archipelagos) for the Sakalava tribe. Several islands and terrestrial features represent a commemoration of this event and are taboos (forbidden to access, etc.).

Rare coral (Turbinaria irregularis).
© Keith Ellenbogen

Fishing community.
© Keith Ellenbogen

Geographic scale, integrity and site type - The overall extent of the northern tip of Madagascar is large, and most likely cannot be reasonably designated as one site. Further, many areas are already degraded. Many of the outstanding locations are small, and can be part of a serial site covering the range of different features discussed here, such as Nosy Hara, Nosy Mitsio, (and possibly Radama Islands), Nosy Tanikely, Ampasindava Bay and mangroves, Ambodivahibe, Loky Bay and Antsiranana Bay

Other sites in the region - Several sites on the west coast and south of Cap St André (from 16°S), and across the northern Mozambique coast, have some similar features, but this region is the only one to have a complete set of all the features and ecosystems, they are the richest ones, and include the most varied geological and oceanographic features.

Key References – Cockcroft & Young (1998); Daniel et al. 1973; Maharavo et al. in press; Maina and Obura (2008); Maina et al. (2008); McKenna and Allen (2005); Obura et al. (2011). --> References